An apparatus of this type is known from an article entitled "Frequenz-Honen fur hohe Abtragraten" [Frequency Honing to Attain High Rates of Removal] in the magazine Werkstatt und Betrieb [Shop and Factory] 118, 1985 (7), pp. 393 to 395 (in particular see p. 394, item 4.1). In the apparatus disclosed, an oscillating relative motion is superimposed on the basic motion of the honing operation, consisting of a rotary motion and an axial reciprocating motion. By means of this motion, an increase in the cutting speed (during the forward stroke) and automatic sharpening of the honing stones (during the backward stroke) is achieved. The oscillation is generated by two hydraulic cylinders. Although more precise information is not available from the article, it can be concluded from this article that the third motion component is a motion with a frequency of at most some 100 Hz. In this case the honing stones are hydro-mechanically pressed on under constant pressure.
A method called "resonant honing" is known from U.S. Pat. No. 2,939,250, which operates with a honing tool the honing bars of which are covered with a coating of abrasive material and are displaceable in a radial direction in that their oblique feed surfaces cooperate with correspondingly oblique feed surfaces of a feed bar. The feed bar is subjected to an oscillating electromagnetic field by means of a coil surrounding it which, as a result of a magnetostriction leads to corresponding periodic shortening or lengthening of the feed bar. Corresponding radial back-and-forth motions of the honing bars via the recited adjustment mechanism are a result of this oscillation. A second exemplary embodiment described in the same reference generates an oscillation between the inner surface of the bore and the stones of the abrasive material coating of the tool by setting the platform on which the workpiece has been fastened into rapid up and down motions. For this purpose the platform has been provided with an oscillation-generating device having a coil excited by an electromagnetic oscillation. In both variants of U.S. Pat. No. 2,939,250, this oscillation is intended to result in the break-down of abrasive grains which have become dull, and thus in an automatic sharpening of the abrasive coating. No information as to frequency is provided; based on the mechanical arrangement, however, it can be assumed that in this case, too, it lies somewhere around 100 Hz. The adjustment device (FIG. 2) or the platform with the workpiece (FIG. 3) illustrated would be too sluggish for higher frequencies.
A method, also with the aim of continuous automatic sharpening of the abrasive coating, is described in U.S. Pat. No. 2,939,251, where the workpiece (see FIG. 2) or the tool (see FIG. 9) is given a third oscillation which lies in the range of 20000 to 100000 Hz, preferably above the audible range, to prevent annoying surrounding noise. In this case, too, there are electromagnetically excited oscillations which are generated by means of coils moving the support for the tool or the workpiece appropriately back and forth. However, the support for the tool or the workpiece does not undergo self-oscillation, it only acts as a rigid means for the transfer of oscillations from the oscillation generator to the tool or the workpiece.
In the course of so-called super-finishing (also: outside honing) in continuous operation, the rotational-symmetrical workpieces are given a rotational motion and on the exterior surface a honing stone is placed, which is given a high-frequency oscillating motion parallel to the rotational axis of the workpiece (see German Patent Publication DE 35 33 082 A1). As a rule the oscillations used in this case have frequencies of up to 3000 oscillations per minute, i.e. of up to 50 Hz. For improving the abrasion of the workpiece it was attempted by means of the method according to the cited reference to proceed in steps and to let the super-finishing stone spark out between the individual steps, each time after a forced feed path.
In connection with super-finishing, i.e. machining the exterior surfaces of rotation-symmetrical workpieces, it has also already been attempted to use ultrasonic waves for cleaning the honing stones (see German Published, Examined Patent Application DE-AS 24 35 848). In this case, however, the ultrasonic oscillation is not forced on the tool, instead it is sprayed via a rinsing liquid as the medium into the surface between the tool and the workpiece in order to increase the removal and flushing of dull or broken-off abrasive grains.
So-called "ultrasonic eroding" does not relate technologically to machining of the interior surfaces of bores, but to drilling of bores in general by means of ultrasonic-generating machining heads. This method has already been combined with drills (see U.S. Pat. Nos. 3,614,484 and 4,828,052). By means of this method it was possible to drill bores into materials which are too hard for normal drilling. However, this does not pertain to finishing of the interior surfaces of already drilled bores.